Gestational choriocarcinoma is a highly malignant epithelial tumor that can be associated with any type of gestational event, most often a complete hydatidiform mole (CM). CM occur in about one per 1000 pregnancies, and about 5-20% of CM progress to invasive moles or choriocarcinoma. Several molecular studies have been done to establish the expression of tumor-associated proteins in choriocarcinoma. In the p53 pathway, overexpression of the p53 protein and the p53-associated protein, MDM2, have been detected. Synergistic upregulation of c-MYC, c-ERB-2, c-FMS, and BCL-2 oncoproteins have also been suggested to have an important role in the pathogenesis of choriocarcinoma. Moreover, choriocarcinomas have been shown to express increased concentrations of MMP and decreased concentrations of TIMP to help with tumor invasion and metastasis.